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a, \(\dfrac{7}{15}\)+\(\dfrac{18}{54}\)
= \(\dfrac{7}{15}\)+ \(\dfrac{1}{3}\)
= \(\dfrac{7}{15}\)+\(\dfrac{5}{15}\)
= \(\dfrac{12}{15}\) = \(\dfrac{4}{5}\) =0,8
b, \(\dfrac{12}{25}\)+\(\dfrac{23}{75}\)-\(\dfrac{1}{4}\)
= \(\dfrac{59}{75}\) -\(\dfrac{1}{4}\)
= \(\dfrac{161}{300}\)
1) a) (-12).12 = -(12.12) = -144
b) 137.(-15) = -(137.15) = - 2 055
2) 5.(-12) = -(5.12) = -60
1,
a, \(\left(\dfrac{-4}{3}+\dfrac{1}{3}\right).\dfrac{5}{12}\)=-\(\dfrac{5}{12}\)
b, \(\dfrac{16}{5}+\left(\dfrac{-45}{14}\right):\dfrac{3}{28}\)
=\(\dfrac{-2}{15}\)
2,
a, 2x+19=25
=>x=3
b, \(-\dfrac{2}{9}x=\dfrac{1}{3}\)
=>x=\(\dfrac{-3}{2}\)
Bài 1:
a) Ta có: \(\dfrac{-4}{3}\cdot\dfrac{5}{12}+\dfrac{1}{3}\cdot\dfrac{5}{12}\)
\(=\dfrac{5}{12}\cdot\left(\dfrac{-4}{3}+\dfrac{1}{3}\right)\)
\(=\dfrac{-5}{12}\)
b) Ta có: \(3\dfrac{1}{5}+\left(\dfrac{2}{7}-\dfrac{7}{2}\right):\dfrac{3}{28}\)
\(=\dfrac{16}{5}+\left(\dfrac{4}{14}-\dfrac{49}{14}\right):\dfrac{3}{28}\)
\(=\dfrac{16}{5}+\dfrac{-45}{14}\cdot\dfrac{28}{3}\)
\(=\dfrac{16}{5}-30=\dfrac{-134}{5}\)
a) 36:32+23.22=9/8+506=(9+506.8)/8=(9+4048)/8=4057/8
b) 3.52-16:22=156-8/11=(156.11-8)/11=(1716-8)/11=1708/11
c) 80-[130-(12-4)2]=80-[130-8.2]=80-[130-16]=80-114=-34
13 - 12 + 11 + 10 - 9 + 8 - 7 - 6 + 5 - 4 + 3 + 2 - 1
= 1 + 11 - 1 + 1 + 11 - 7 + 1
= 12 - 1 + 1 + 11 - 7 + 1
= 11 + 1 + 11 - 7 + 1
= 12 + 11 - 7 + 1
= 23 - 7 + 1
= 16 + 1
=17
a)12-12:4+3=12-(12:4)+3 b)(26,37+14,37)-2,37=40,74-2,37
=12-3+3 =38,01
=9+3
=12